Research from Italy on the dietary protein supply for heavy finishers reveals that lowering the protein content does not impair carcass quality.

The effects of dietary protein supply on heavy pig carcass quality have been investigated by Luigi Gallo and colleagues at the University of Padova and reported in Livestock Science.

They found that the diets, which differed in crude protein and essential amino acids, affected neither the weights or yields of commercial cuts nor the uniformity of carcass, loin and ham weights.

Lowering the protein content of finishing heavy pigs diet does not impair carcass quality, they concluded.

This study investigated the effects of four dietary treatments characterized by 0 to 20 per cent progressive reduction of the dietary crude protein (CP) and indispensable amino acid (AA) contents on carcass quality and uniformity of pigs fed restrictively and slaughtered around 165kg bodyweight.

Carcass data from 233 pigs from a feeding study that involved three batches of 80 crossbred pigs each were used.

Pigs, the progeny of 12 boars, were assigned to one of four dietary treatments (10 pigs per pen, gilts and barrows, and two pens per treatment in each batch) with diets formulated to contain 146 to 117 and 133 to 108g per kg of CP and 7.3 to 5.8 and 5.7 to 4.7g per kg of total lysine in early (90 to 130kg) and late (130 to 165kg) finishing, respectively.

After slaughter, the carcasses were processed and the weight of the commercial lean (neck, loin, shoulder and ham) and fat cuts (backfat, belly and jowl) was recorded.

The coefficient of variation was used to describe uniformity of the most important carcass traits, and the corresponding confidence intervals were computed to make comparisons across dietary treatments.

Carcass weight and midline backfat thickness averaged 137kg and 31mm, respectively, and were not affected by diets.

Diets did not influence the weight of commercial cuts and their proportion on carcass weight, with the sole exception of loins. Pigs fed diets containing the two lowest CP content had a slight lower proportion of loins in the carcass compared with pigs fed the conventional CP diet (P<0.05).

Most carcass traits were affected by sex and by sire effects but interactions between diet and sex or sire were inconsistent.

Uniformity of carcass weight, backfat thickness and weight of loins and dressed hams was not influenced by the dietary treatments.

Gallo and colleagues concluded that the content of CP, lysine and other indispensable AA of conventional diets for finishing heavy pigs may be reduced by 20 per cent without impairing the weight of carcass and primal cuts and the yields of dressed hams.

This feeding strategy they added, will contribute to the heavy pig industry by reducing feed costs (i.e. decreasing the dietary provision of soybean meal and crystalline amino acids) and minimising nitrogen excretion, without affecting carcass quality.